CoPc and CoPcF16 on gold: Site-specific charge-transfer processes

Interface properties of cobalt(II) phthalocyanine (CoPc) and cobalt(II) hexadecafluoro-phthalocyanine (CoPcF16) to gold are investigated by photo-excited electron spectroscopies (X-ray photoemission spectroscopy (XPS), ultraviolet photoemission spectroscopy (UPS) and X-ray excited Auger electron spectroscopy (XAES)). It is shown that a bidirectional charge transfer determines the interface energetics for CoPc and CoPcF16 on Au. Combined XPS and XAES measurements allow for the separation of chemical shifts based on different local charges at the considered atom caused by polarization effects. This facilitates a detailed discussion of energetic shifts of core level spectra. The data allow the discussion of site-specific charge-transfer processes.

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Characterization of Charge States in Conducting Organic Nanoparticles by X-ray Photoemission Spectroscopy

Materials ◽

10.3390/ma14082058 ◽

2021 ◽

Vol 14 (8) ◽

pp. 2058

Author(s):

Jordi Fraxedas ◽

Antje Vollmer ◽

Norbert Koch ◽

Dominique de Caro ◽

Kane Jacob ◽

...

Keyword(s):

Partial Oxidation ◽

Chemical Shifts ◽

Large Family ◽

Photoemission Spectroscopy ◽

Intrinsic Structure ◽

X Ray ◽

Level Lines ◽

Donor And Acceptor ◽

Electronic Configurations

The metallic and semiconducting character of a large family of organic materials based on the electron donor molecule tetrathiafulvalene (TTF) is rooted in the partial oxidation (charge transfer or mixed valency) of TTF derivatives leading to partially filled molecular orbital-based electronic bands. The intrinsic structure of such complexes, with segregated donor and acceptor molecular chains or planes, leads to anisotropic electronic properties (quasi one-dimensional or two-dimensional) and morphology (needle-like or platelet-like crystals). Recently, such materials have been synthesized as nanoparticles by intentionally frustrating the intrinsic anisotropic growth. X-ray photoemission spectroscopy (XPS) has emerged as a valuable technique to characterize the transfer of charge due to its ability to discriminate the different chemical environments or electronic configurations manifested by chemical shifts of core level lines in high-resolution spectra. Since the photoemission process is inherently fast (well below the femtosecond time scale), dynamic processes can be efficiently explored. We determine here the fingerprint of partial oxidation on the photoemission lines of nanoparticles of selected TTF-based conductors.

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Layer-resolved many-electron interactions in delafossite PdCoO2 from standing-wave photoemission spectroscopy

Communications Physics ◽

10.1038/s42005-021-00643-y ◽

2021 ◽

Vol 4 (1) ◽

Author(s):

Qiyang Lu ◽

Henrique Martins ◽

Juhan Matthias Kahk ◽

Gaurab Rimal ◽

Seongshik Oh ◽

...

Keyword(s):

Charge Transfer ◽

Standing Wave ◽

Three Dimensional ◽

Photoemission Spectroscopy ◽

Electronic Coupling ◽

Many Body ◽

X Ray ◽

Charge Transfer Excitons ◽

Many Body Interactions ◽

Electron Interactions

AbstractWhen a three-dimensional material is constructed by stacking different two-dimensional layers into an ordered structure, new and unique physical properties can emerge. An example is the delafossite PdCoO2, which consists of alternating layers of metallic Pd and Mott-insulating CoO2 sheets. To understand the nature of the electronic coupling between the layers that gives rise to the unique properties of PdCoO2, we revealed its layer-resolved electronic structure combining standing-wave X-ray photoemission spectroscopy and ab initio many-body calculations. Experimentally, we have decomposed the measured VB spectrum into contributions from Pd and CoO2 layers. Computationally, we find that many-body interactions in Pd and CoO2 layers are highly different. Holes in the CoO2 layer interact strongly with charge-transfer excitons in the same layer, whereas holes in the Pd layer couple to plasmons in the Pd layer. Interestingly, we find that holes in states hybridized across both layers couple to both types of excitations (charge-transfer excitons or plasmons), with the intensity of photoemission satellites being proportional to the projection of the state onto a given layer. This establishes satellites as a sensitive probe for inter-layer hybridization. These findings pave the way towards a better understanding of complex many-electron interactions in layered quantum materials.

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Evaluation of ITO/a-Si interface properties by hard X-ray photoemission spectroscopy

2018 IEEE 7th World Conference on Photovoltaic Energy Conversion (WCPEC) (A Joint Conference of 45th IEEE PVSC, 28th PVSEC & 34th EU PVSEC) ◽

10.1109/pvsc.2018.8548139 ◽

2018 ◽

Author(s):

Tappei Nishihara ◽

Takuto Kojima ◽

Takuya Hiyama ◽

Hideki Matsumura ◽

Takefumi Kamioka ◽

...

Keyword(s):

Photoemission Spectroscopy ◽

Interface Properties ◽

X Ray

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The interface between chloroaluminum phthalocyanine and titanium dioxide: The influence of surface defects and substrate termination

Physical Chemistry Chemical Physics ◽

10.1039/d1cp01638e ◽

2021 ◽

Author(s):

Małgorzata Polek ◽

Tamara Basova ◽

Thomas Chassé ◽

Heiko Peisert

Keyword(s):

Titanium Dioxide ◽

Surface Defects ◽

Photoemission Spectroscopy ◽

Interface Properties ◽

Crystal Surfaces ◽

Single Crystal Surfaces ◽

X Ray ◽

Ultraviolet Photoemission Spectroscopy ◽

Chloroaluminum Phthalocyanine ◽

Rutile Titanium Dioxide

Interface properties of chloroaluminum(III) phthalocyanine (AlClPc) on two different rutile titanium dioxide (TiO2) single crystal surfaces ((100) and (001)) have been studied using X-ray and ultraviolet photoemission spectroscopy (XPS and...

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Interface atom mobility and charge transfer effects on CuO and Cu2O formation on Cu3Pd(111) and Cu3Pt(111)

Scientific Reports ◽

10.1038/s41598-021-82180-w ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Yasutaka Tsuda ◽

Jessiel Siaron Gueriba ◽

Takamasa Makino ◽

Wilson Agerico Diño ◽

Akitaka Yoshigoe ◽

...

Keyword(s):

Charge Transfer ◽

Synchrotron Radiation ◽

Surface Temperature ◽

Molecular Beam ◽

Photoemission Spectroscopy ◽

Oxide Surfaces ◽

Oxide Formation ◽

Transfer Effects ◽

X Ray

AbstractWe bombarded $$\mbox{$\text{Cu}_{3}\text{Pd}(111)$}$$ Cu 3 Pd ( 111 ) and $$\mbox{$\text{Cu}_{3}\text{Pt}(111)$}$$ Cu 3 Pt ( 111 ) with a 2.3 eV hyperthermal oxygen molecular beam (HOMB) source, and characterized the corresponding (oxide) surfaces with synchrotron-radiation X-ray photoemission spectroscopy (SR-XPS). At $$300\,\text{K}$$ 300 K , CuO forms on both $$\mbox{$\text{Cu}_{3}\text{Pd}(111)$}$$ Cu 3 Pd ( 111 ) and $$\mbox{$\text{Cu}_{3}\text{Pt}(111)$}$$ Cu 3 Pt ( 111 ) . When we increase the surface temperature to $$500\,\text{K}$$ 500 K , $$\mbox{$\text{Cu}_{2}\text{O}$}$$ Cu 2 O also forms on $$\mbox{$\text{Cu}_{3}\text{Pd}(111)$}$$ Cu 3 Pd ( 111 ) , but not on $$\mbox{$\text{Cu}_{3}\text{Pt}(111)$}$$ Cu 3 Pt ( 111 ) . For comparison, $$\mbox{$\text{Cu}_{2}\text{O}$}$$ Cu 2 O forms even at $$300\,\text{K}$$ 300 K on Cu(111). On $$\mbox{$\text{Cu}_{3}\text{Au}(111)$}$$ Cu 3 Au ( 111 ) , $$\mbox{$\text{Cu}_{2}\text{O}$}$$ Cu 2 O forms only after $$500\,\text{K}$$ 500 K , and no oxides can be found at $$300\,\text{K}$$ 300 K . We ascribe this difference in Cu oxide formation to the mobility of the interfacial species (Cu/Pd/Pt) and charge transfer between the surface Cu oxides and subsurface species (Cu/Pd/Pt).

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X-ray Photoemission Spectroscopy Study of Uniaxial Magnetic Anisotropy Induced in a Ni Layer Deposited on a LiNbO3 Substrate

Nanomaterials ◽

10.3390/nano11041024 ◽

2021 ◽

Vol 11 (4) ◽

pp. 1024

Author(s):

Akinobu Yamaguchi ◽

Takuo Ohkochi ◽

Masaki Oura ◽

Keisuke Yamada ◽

Tsunemasa Saiki ◽

...

Keyword(s):

Binding Energy ◽

Magnetic Anisotropy ◽

Chemical Shifts ◽

Ferromagnetic Layer ◽

Magnetic Domain ◽

Ferroelectric Materials ◽

Photoemission Spectroscopy ◽

Uniaxial Magnetic Anisotropy ◽

X Ray ◽

Domain Structures

The competition between magnetic shape anisotropy and the induced uniaxial magnetic anisotropy in the heterojunction between a ferromagnetic layer and a ferroelectric substrate serves to control magnetic domain structures as well as magnetization reversal characteristics. The uniaxial magnetic anisotropy, originating from the symmetry breaking effect in the heterojunction, plays a significant role in modifying the characteristics of magnetization dynamics. Magnetoelastic phenomena are known to generate uniaxial magnetic anisotropy; however, the interfacial electronic states that may contribute to the uniaxial magnetic anisotropy have not yet been adequately investigated. Here, we report experimental evidence concerning the binding energy change in the ferromagnetic layer/ferroelectric substrate heterojunction using X-ray photoemission spectroscopy. The binding energy shifts, corresponding to the chemical shifts, reveal the binding states near the interface. Our results shed light on the origin of the uniaxial magnetic anisotropy induced from the heterojunction. This knowledge can provide a means for the simultaneous control of magnetism, mechanics, and electronics in a nano/microsystem consisting of ferromagnetic/ferroelectric materials.

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